Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WO 2UU4JE112931 PCTlUS211031023955
Aaoustical xnsulation Laamiaate -Pith Polyoletin Layer and
Procrsa for Makin4
by
etatthax Barqo II
BAGKGRG= OF 778a INVISNTION
The present invention relates to an acoustical insulation
laminate product and more specifically to an acoustical
insulation laminate product ccanprising an acoustical
insulation mat or absorbing material, a polyolefin face,
backing, or both, and a firont and back face cloth which
increase the total noise reduction coefficient.
The use of fiberglass in the manufacturing of acoustical
and insulation products is well known. Moreover, insulation
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materials comprised of fiberglass and organic fibers,
including cotton, as well as synthetic or man-made fibers,
formed into mats and utilizing a thermo-setting resin have
been utilized for many years in the manufacturing of
insulation and acoustical products. For example, U.S. Patent
No. 2,689,199 teaches the use of thermoplastic polymers and
refractory fibers of glass in the manufacture of a non-woven
porous flexible fabric and U.S. Patent No. 2,695,855 teaches
the use of cotton, rayon, nylon or glass fibers with an
appropriate resin for a thermal or acoustical insulation
material. And, U.S. Patent No. 4,888,235 teaches a non-woven
fibrous product comprising a blended matrix of glass fibers
and synthetic fibers having a conductive material of powdered
aluminum, copper or carbon black and a thermo-setting resin
dispersed in the matrix. However, a number of these
insulation products which contain glass fibers and synthetic
fibers are generally brittle and are easily broken or cracked
when subjected to excessive flexing during installation or
use. Moreover, these acoustic insulation products generally
absorb high frequencies well but do not absorb low frequencies
as well.
There are generally three types of fiberglass which may
be used to make the acoustical insulation. The first two
types are known as rotary and flame-attenuated fiberglass
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which are generally formed of about 5 microns or less diameter
glass fiber strands, but may exceed 5 microns depending on the
application. The third type of fiberglass is typically known
as continuous strand or textile fiberglass and generally has a
diameter of greater than 5 microns. Comparing the three
types, the first two products are typically more expensive to
produce, historically have better sound absorption
characteristics, but cause more irritation to human skin, are
more respirable due to their smaller diameter and therefore
are more of a health hazard. And, although the smaller
diameter allows for greater density which corresponds to its
ability to absorb sound, the smaller diameter results in less
durability. On the other hand, the textile fiberglass is
typically stronger, more durable, and less hazardous to
humans.
Although the fiberglass acoustical insulation and most
other sound absorbers typically work well for higher frequency
sounds above about 2500 Hz, the lower range frequencies are
more difficult to absorb. Frequencies less than about 2500 Hz
often pass through known fiberglass acoustical insulations
which is highly undesirable in, for instance, an automobile.
Non-porous polyfilms have been used with acoustical
absorbing materials in order to absorb limited specific
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frequencies rather than a wider range of frequencies.
However, this is not useful in situations where an enclosure
is bombarded by a wide range of acoustical frequencies.
Moreover, the polyfilm, which typically absorbs low frequency
sounds, dramatically decreases the ability of the sound
absorption material to absorb high frequency sounds.
In view of the deficiencies in known acoustical
laminates, it is apparent that an acoustical laminate is
needed which effectively absorbs both high range frequencies
and low range frequencies, is cost effective, lightweight,
durable, and stronger than known acoustical absorbing
materials.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an
improved acoustical insulation laminate comprising an
acoustical insulation mat and a polyolefin film having equal
or greater performance than existing absorbing material at a
lighter weight.
It is a further object of the present invention to
provide an acoustical insulation laminate with a wide range of
frequency absorption.
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It is yet an even further object to provide an acoustical
insulation for automobiles, which are lighter in weight than
other acoustic insulations, thereby improving gas mileage and
reducing automobile operating expense.
It is still a further object to provide a porous polyfilm
in combination with and which enhances known acoustical sound
absorbers such as fiberglass, cotton, synthetic, cotton-
synthetic blends other acoustical absorbers whether man-made
or natural in order to provide an equal or greater range of
sound absorption.
It is also an object of the present invention to provide
a highly effective sound absorbing laminate using recycled raw
materials that are economical to produce.
It is still an even further object of the present
invention to provide a polyolefin film having a total flow-
through opening of at least 0.25 percent of the surface area
of the film, and preferably between 0.25 percent and 50
percent of the surface area of the film.
Even one further object of the present invention is to
provide a process for forming the acoustical laminate having a
porous polyolefin layer.
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More particularly, the acoustical insulation laminate of
the present invention includes an insulation mat or absorbing
material and a porous polyfilm or polyolefin film. One
example of an absorbing material that may be used in the
present invention is a fiberglass fibrous material with nylon
and a thermo-setting resin co-binder. An example of such a
fiberglass mat is set forth in U.S. Patent Number 5,883,020
issued to Bargo et al. and is incorporated herein by
reference.
The instant invention further includes at least one layer
of porous polyolefin film or polyfilm affixed to the
acoustical insulation mat in order to absorb the lower range
frequencies that the acoustical insulation mat typically does
not absorb well. The polyfilm typically acts as a barrier to
high frequency sounds, however, the porous nature of the
polyfilm of the instant invention allows the polyfilm to act
as an absorber for low frequency sound, yet allows a wide
range of higher frequency sounds to pass through to the
absorbing material wherein prior polyfilm laminates have
failed. The polyfilm may be a thermo-setting plastic so that
the polyfilm thermally bonds to the acoustical insulation mat.
Alternatively, the polyfilm may be applied to the acoustical
insulation mat with the use of resins, co-polymers, polyesters
and other thermoplastic materials. The polyfilm is preferably
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comprised of a polyolefin, particularly a polypropylene or
polyethylene and should be positioned between the sound source
and the acoustical insulation mat so that the film resonates
against the absorbing material to destroy acoustical energy of
the low frequency sound. The polyfilm preferably has a
plurality of spaced acoustical flow-through openings allowing
high frequency sounds to pass therethrough and be absorbed by
the acoustical insulation mat. The surface area of the at
least one acoustical flow-through opening may be between 0.25
percent and 50.0 percent. Prior to molding, the acoustical
flow-through openings may be circular, square, or any other
pre-selected geometric shape including slits. And, upon
molding, the polyfilm comprises multiple random shaped
apertures having various shapes, sizes, and areas permitting
the film to absorb low frequency sounds and permitting high
frequency sounds to pass through and be absorbed by the
acoustical absorbing material. In operation the polyfilm
absorbs low frequency sounds by resonating and destroying
acoustical energy while reflecting some high frequency sounds.
Other high frequency range sounds passing through the
acoustical flow-through openings are absorbed by the
acoustical insulation mat. The polyfilm may be used with
known rotary, flame-attenuated, or textile fiberglass
absorbers as well as other acoustical absorbers in order to
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enhance their ability to absorb a wide frequency range of
sounds.
Finally the acoustical insulation laminate may include a
face cloth extending over the film. The face cloth helps
retain the laminate together and provides an aesthetically
pleasing appearance. The face cloth also affects the amount
of distortion of the polyfilm apertures and therefore the
performance of the polyfilm.
All of the above outlined objectives are to be understood
as exemplary only and many more objectives of the invention
may be gleaned from the disclosure herein. Therefore, no
limiting interpretation of the objectives noted is to be
understood without further reading of the entire
specification, claims, and drawings included herewith.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a perspective view of the acoustical
insulation laminate of the present invention;
FIG. 2 shows a sectional view of the acoustical
insulation laminate of Fig. 1 further including a face cloth;
and,
FIG. 3 shows a chart display of the absorption
coefficient of both a fiberglass acoustic insulation and a
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fiberglass acoustical insulation with a porous polyolefin
film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the present invention as shown in
Figs. 1 and 2, an acoustical insulation laminate 10 is
provided herein having at least a front and a rear surface.
The acoustical insulation laminate 10 includes an acoustical
insulation or sound absorbing material mat 12, a polyolefin
film 14 having at least one acoustical flow-through opening
16, and preferably a face cloth 18. The acoustical insulation
mat 12 has a front and a rear surface, is preferably formed of
fiberglass, and may vary in weight and thickness in order to
vary the frequency absorption characteristics. A preferred
fiberglass mat will be from 2 mm to 155 mm in thickness and
the film will be from about .2 mil to 20 mils in thickness.
Moreover, the cross-sectional area of the openings 16, prior
to molding, will be from .10 to 25.4 millimeters square (mm2)
and spaced throughout the film. The textile fiberglass
fibers, preferably from less than 12.7 mm to about 127 mm in
length and greater than 5 microns in diameter, are combined to
form an acoustic insulation mat 12. And, although it is
within the scope of this invention to use flame attenuated or
rotary fiberglass strands, it is preferable to use textile
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fiberglass which is more durable, less irritable, more
economical and therefore preferred in a plurality of
applications including for instance the automotive industry.
The acoustical insulation mat 12 may also include recycled
scrap nylon and resins as co-binders for holding the
fiberglass particles in mat form. When the acoustical
insulation mat 12 is formed of fiberglass, the mat 12 is
typically a good acoustical insulator for frequency ranges
above about 2500 hertz (Hz) but is not as effective at
frequencies below 2500 Hz. One such mat is described in U.S.
Patent Number 5,883,020 issued to Bargo et al.
In the manufacture of a product of the present invention,
a fiber-binder complex mix is formed and a sheet of porous
polyolefin film or polyfilm 14 is stretched over a planar
section of the insulation mat 12 and slightly preheated to at
least about 220 degrees Fahrenheit, for a polyethylene, to
tack the mat 12 and polyfilm 14 together. However, various
other temperatures may be utilized to secure the polyfilm 12
to the insulation mat 12 prior to molding or curing. The face
cloth 18 may also be added before the tacking occurs. The
porous polyfilm 14 is comprised of a polyolefin, particularly
polyethylene or polypropylene, which bonds to the fiberglass
acoustic insulation 12 by application of heat and may be
applied to a face, a backing, or both depending on the desired
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sound characteristics. Application of heat and pressure
stretches the polyfilm 14 resulting in multiple varying
densities throughout the polyfilm 14. The multiple varying
densities enhance the ability of the polyfilm 14 to resonate
at varying frequencies and therefore absorb more acoustical
energy. In accordance with a preferred embodiment, the
polyfilm 14 is positioned on the insulation mat 12 and facing
a sound source. The porous polyfilm 14 has at least one
acoustical flow-through opening between about 0.25 percent and
50.0 percent of the total surface area of the polyfilm 14.
Preferably, the total surface area of the at least one
acoustical flow-through opening 16 is formed by a plurality of
small acoustical flow-through openings 16 which, when
combined, make up a total open area of between about 0.25 and
50.0 percent of the surface area of the acoustical insulation
laminate 10 after molding. The plurality of acoustical flow-
through openings 16 may be in a spaced configuration and the
initial openings 16, prior to molding, may be a plurality of
shapes for example square, circular, or slits. The polyfilm
14 may vary in thickness ranging from .2 mil to 20 mils and
may also vary in weight to absorb various ranges of
frequencies. The porous polyfilm 14 may be between .5 and
40.0 percent by weight of the laminate 10.
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In accordance with one embodiment of the instant
invention, the porous polyfilm 14 absorbs frequencies below
about 2500 Hz better than the insulation mat 12 alone and,
when used in combination with the sound absorbing material,
the laminate 10 raises the total noise reduction coefficient
as compared to insulation mat alone. As shown in Fig. 3, a
chart is depicted showing a comparison of frequency versus
absorption coefficient for two acoustical materials. Line 1
represents coefficient of absorption of the fiberglass
insulation alone while line 2 represents the fiberglass
insulation with the porous polyfilm 14 applied thereto. As
discussed above it is desirable to absorb more sound having a
frequency less than about 2500 Hz. This is represented as an
increase in the coefficient of absorption along the vertical
line of the chart. By adding the polyfilm 14 to the
fiberglass insulation, line 2 of the chart shows an increase
in absorption between about 125 Hz and 2500 Hz. In this
example, the fiberglass mat is approximately 23.4 millimeters
in thickness, the polyfilm is a polyethylene film with an
initial thickness of about 2 mils prior to molding, and the
apertures in the film initially have a cross-sectional area of
about .10 to 25.4 square millimeters (mm2). The acoustical
flow-through apertures 16 are distributed over the film,
initially taking up between approximately .25 and 15 percent
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of the surface area of the film. Larger openings grow less
than smaller openings during curing or molding and the
individual growth percentages are affected by the position of
the film 14 in the mold and the stress on the film 14. After
curing or molding, the apertures 16 may grow individually in
stress relieving directions between about 0 and 600 percent
such that the percentage of total opening of the surface area
of the film 14 is between about 1.75 and 15 percent. However,
this growth percentage is exemplary and may vary to other
ranges. By changing the surface area of the flow-through
openings 16, the ratio of the openings to the solid film 14,
and the thickness of the polyfilm 14, the coefficient of
absorption may vary for frequencies both greater than and less
than 2500 Hz. Moreover, by changing the weight and thickness
of the laminate 10, the absorption characteristics may be
adjusted to absorb desired frequencies. Finally, it should be
understood by one of ordinary skill in the art that the porous
polyfilm 14 may be used with any sound absorbent material
including fiberglass, cotton, synthetics, cotton-synthetic
blends, and other acoustical absorbers which may be of the
natural or man-made variety to provide equal or greater
performance than the absorbent material alone.
The apertures 16 of the porous polyfilm 14 play an
important role in absorbing a wide range of low frequencies
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with the polyfilm instead of a very specific limited range as
prior art polyfilms. In forming the porous polyfilm 16, a
plurality of spaced apertures 16 are placed in the polyolefin
film 16. The apertures, as discussed above may be from .10 to
25.4 square millimeters (mm2) and may be arranged in a
uniformly spaced pattern. The porous polyfilm 14 is stretched
over the absorbing material 12 with the application of heat
which non-uniformly varies the density of the polyfilm 14 by
becoming thinner and increases the area of the at least one
aperture 16.
As shown in Fig. 2, a face cloth 18 may also be applied
to the acoustic insulation mat 12 and polyfilm 14. The face
cloth 18 may be comprised of about 70% polyester and 30%
rayon, pure polyester, or various other combinations known to
one of ordinary skill in the art. The face cloth 18 assists
in maintaining the laminate of fiberglass 12 and polyfilm 14
together as well as improving aesthetic appearance. However,
the face cloth 18 is not essential to the instant invention.
The face cloth 18 may be applied with a thermo-setting resin
or a thermoplastic so as to adhere to the fiberglass acoustic
insulation 12 and the polyfilm 14.
Once the initial flow-through openings 16 are formed, the
polyfilm 14 is stretched over the acoustical insulation mat
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12. Next the face cloth 18 may be applied on a front, rear, or
preferably both. The porous polyfilm 14 and face cloth 18 may
be heated in a curing oven, by infrared, or by a hot-rolling
process to tack the polyfilm 14 insulation mat 12 and face
cloth 18 together. The acoustical insulation laminate 10 is
subjected to sufficient heat to at least cure and set a
desired proportion of the thermo-setting resin. In the
production of a cured ductliner typically using a phenolic
resin binder, the temperature of the oven will range from 250
to 700 degrees Fahrenheit, depending upon the thickness and
gram weight of the mat being produced. And, the acoustical
insulation laminate 10 is subjected to these temperatures for
a period of time sufficient to set the phenolic resin binder,
which is from about 15 seconds to 4 minutes. In the
production of a semi-cured laminate 10 to be further subjected
to a molding operation, the temperature of the oven will range
from 200 to 500 degrees Fahrenheit for from 15 seconds to 3
minutes so that the phenolic resin is only partially set. The
cured or semi-cured laminate 10 leaving the curing oven may
pass through a cooling chamber and then through a slitter
where the slitter slits the laminate 10 into sections of a
pre-selected width and length. The laminate 10 is then
transferred by conveyor to storage for further use.
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The acoustical laminate 10 may be formed in a plurality
of ways including a hot molding and a cold molding process. In
the mold operation the laminate 10 will be completely cured
and set into a desired shape and thickness. In a hot molding
process various combinations of the sound absorbing material
12, the porous polyfilm 14, and the face cloth 18 may be used
to form a laminate. For instance, a face cloth 18 and
polyfilm 14 may form a laminate, or a sound absorbing material
12 and polyfilm 14 may form a laminate, or the sound absorbing
material 12, the polyfilm 14, and at least one face cloth 18,
preferably two face cloths 18 may form a laminate.
Various combinations of these elements may be layered on
material handling equipment such as a traditional conveyor or
a roller-link chain conveyor for molding and formation of the
laminate. The layering may be performed by continuously
pulling the elements of laminate 10 from rolls, called roll-
loading. In the alternative the laminate elements may come in
pre-cut blanks in which case the laminate elements may be
stacked on material handling equipment for movement into a
mold cavity.
After the material is aligned, the material handling
equipment indexes or advances the elements of the laminate
into a mold cavity. In the alternative, the elements of the
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laminate may be loaded by hand into the mold cavity. In the
hot molding process the mold cavity is heated to a desired
temperature so that during the molding process a thermoset
resin having a pre-selected activation temperature is
activated. Any or all of the elements forming the laminate 10
may have the thermoset resin or a thermoplastic, or both
therein so that whichever element has the lowest activation
temperature is activated first when that element reaches its
activation temperature. Alternatively, all of the elements of
the laminate may have the same activation temperature.
Heat may be provided to the mold cavity in a plurality of
methods including hot forced air provided by gas combustion,
electric heat, infrared heating, radiant heating, or heated
thermal fluids. The mold temperature should be higher than
the desired activation temperature to account for heat loss
from the mold and the like. The activation temperature of the
thermoset resin may be between about 120 and 500 degrees.
Once the layered laminate elements are positioned in the
mold cavity, the mold press applies pressure. Any type of mold
known in the art may be used such as fluid operated preferably
by hydraulics or air, rotary molds, double shuttle molds, non-
shuttle molds and roll loader molds. The molding pressure may
vary be at least one pound per square inch and the cycle time
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required in the mold may vary between about 15 seconds and 3
minutes and is determined by the density and weight of the
laminate elements. The result is a laminate 10 comprising a
sound absorbing material 12, a porous polyolefin film 14, and
preferably at least one face cloth 18 preferably having a
thickness of between about 2 and 155 millimeters.
During the curing or molding process, the application of
heat causes the thermo-plastic polyfilm 14 to further stretch
and non-uniformly vary the density. However, since the
polyfilm 14 is attached to the face cloth 18 and the absorbing
material 12, distortion of the polyfilm 14 occurs at a
different rate than the insulation mat 12 and face cloth 18
due to the relationship between the heat and pressure applied
and the differing densities and thickness of the materials.
This causes the distortion of the acoustical flow-through
apertures 16 and varying polyfilm 16 densities. The result is
a plurality of multiple random shaped apertures 16 which allow
high frequency sounds to pass through to the absorbing
material 12. In addition, the change in density increases the
ability of the laminate 10 to resonate at various frequency
ranges.
In the alternative, the laminate 10 may also be molded in
a cold molding process. In this process, the insulation mat
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12 may be produced with a thermoplastic instead of a thermoset
resin. In cold molding the laminate elements are aligned and
indexed or advanced by a roll-loading process, advancing of
pre-formed blanks, or manually loaded by hand. The laminate
elements are then heated to an activation temperature of
between about 120 and 500 degrees Fahrenheit. Next the
laminate elements are placed in a cooled mold which lowers the
temperature of the thermoplastic to below the activation
temperature. The mold may be cooled by ambient air, by water,
or by a chiller system. Within the cooled mold pressure is
applied in an amount ranging from about 1 to 100 pounds per
square inch. After cold molding or hot molding the laminate
10 may be cut to any preselected size and shape.
In use the acoustical laminate 10 is placed about an
enclosure where sound absorption is desired. In accordance
with a preferred embodiment of the present invention, the
polyolefin film 14 is placed between the sound source and the
acoustic insulation mat 12. The plurality of acoustical flow
through apertures 16 allow frequencies above about 2500 Hz to
pass therethrough to the insulation mat 12 while many
frequencies above 2500 Hz may be reflected by the polyfilm 14.
Meanwhile, frequencies below about 2500 Hz, which would not be
absorbed by the insulation mat 12, are absorbed by the
polyfilm layer.
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Even though only one preferred embodiment has been shown
and described, it is apparent those products incorporating
modifications and variations of the preferred embodiment will
become obvious to those skilled in the art and therefore the
described preferred embodiment should not be construed to be
limited thereby.
